1. Technical Field
The present invention relates to a semiconductor light emitting device and particularly to the electrode structure of a light emitting diode (hereinafter referred to as an LED).
2. Description of the Related Art
FIGS. 1A and 1B show the structure of a conventional LED chip 100. Refer to, for example, Japanese Patent Application Laid-Open Publication No. 2001-345480. The LED chip 100 has a sapphire substrate 101, an n-layer 102, a light emitting layer 103, a p-layer 104, a transparent electrode 105, an n-electrode 106 formed on the n-layer 102, and a p-electrode 107 formed on the transparent electrode 105. Because the p-layer 104 is lower in conductivity and thinner in film thickness than the n-layer 102, current is difficult to be diffused in planar directions of the LED chip in the p-layer. Hence, the transparent electrode 105, which makes the current diffuse in planar directions and allows light from the light emitting layer 103 to pass therethrough, is provided on the surface of the p-layer 104. By providing the transparent electrode 105 between the p-layer 104 and the p-electrode 107, a light emission driving current is made to be diffused in planar directions of the LED chip 100, and thus the in-plane uniformity of light emission brightness distribution can be improved. However, only with the transparent electrode being provided, that effect is not enough, and current concentration and light emission concentration will occur in the peripheries of the p-electrode and the n-electrode and in the vicinity of a straight line joining these electrodes. Accordingly, the n-electrode 106 and the p-electrode 107 each have an auxiliary electrode. Specifically, the n-electrode 106 comprises an n-pad portion 106a and comb tooth-shaped n-auxiliary electrodes 106b connected thereto, and the p-electrode 107 includes a p-pad portion 107a and comb tooth-shaped p-auxiliary electrodes 107b connected thereto. By making the distance between the n-auxiliary electrodes 106b and the p-auxiliary electrodes 107b constant, the density of the light emission driving current flowing between these electrodes becomes uniform, and thus the light emission brightness distribution can be made uniform across the LED chip surface.